Nanoscale electrical contacts have attracted substantial attention due to the advancements in nanotechnology, material sciences and growing demands for miniaturization of electronic devices and high packing density. Contact resistance and their electro-thermal effects have become one of the most critical concerns of very large scale integration (VLSI) circuit designers because of the excessive amount of Joule heating being deposited at the contact region. The growing popularity of novel electronic circuits based on graphene, carbon nanotubes (CNTs), new two-dimensional (2D) materials (boron nitride, molybedenum sulfide, black phosphorus, etc.), and new nano-composites has made contact engineering crucial. To improve reliability and lifetime of a device with nanoscale contacts, control of the electrical properties in the contact area is critical, which can open doors for new device opportunities.
Tunneling type of electrical contacts have become ubiquitous for novel materials based devices, where the contacting members are separated by very thin (˜1 nm or less) insulating layers. For example, tunneling effects in contact junctions dictate the electrical conductivity of the CNT/polymer composite thin films. Tunneling resistance also plays a dominant role in the electrical conductivity of CNT-based polymeric or ceramic composites.
For decades, the basic models of tunneling current between electrodes separated by thin insulating films have been those of Simmons in 1960s. Simmon's formula have since been used for evaluating tunneling current in tunneling junctions. Though there have been attempts to extend Simmons' models to the field emission and space-charge-limited regimes, existing models always assume that the tunneling junctions are one-dimensional (1D); therefore, there are no variations on the voltage drops along the length of the tunneling junction and the insulating film thickness is uniform.
Thus, these existing models of tunneling junctions provide no insight regarding the variation of tunneling current along the contact length and ignore the importance of current crowding near the contact area when the two contacting members are partially overlapping. More importantly, there is generally a lacking of a method to precisely control the current crowding effects in nanoscale electrical contacts to improve heat management and increase reliability and lifetime of electronics.
This section provides background information related to the present disclosure which is not necessarily prior art.